Automatic feed for drills



19, 1946- A. E. SHERMAN 2,395,018

AUTOMATIC FEED FOR DRILLS Filed Feb. 28, 1944 as I I 1 h I y l w 9 P- v I N l- I 8 a 4 mmvrog; -4 i To ARTHUR ESHERMAN ATTORNEYS Patented Feb. 19, 194

AUTOMATIC FEED Fort-palms Arthur E. Sherman, Detroit, ien, assignorto Briggs Manufacturing Company, Detroit, Mich.,

a corporation of Michigan I 7 Application February 28, 1944', Serial No.j524,342 L 3 Claims. (01. 77 -32) This invention relates to pneumatic tools, and more particularly to pneumatically-operated manually-controlled drill In the'pre'sent state of the art, it has been found desirable both .from economicand production standpoints to use portable air-operated 'tools for drilling holes in the various places required in the parts which are to be assembled into a finished structurer Particularly is this so where the parts areof comparatively. large size and irregular shape so that the design and construction of a drilling machine not utilizing port able drills would entail high tooling costs and initial delay in production. One of the disadvantages of the use of portable drills is that accuracy is dependent upon the skill and attentive- "ness of the'human operato with the result that the drill holes are often misaligned. Furthermore,

the feed of a portable drill depends upon the pressure applied by the operator, which if too great may result in damaging the work or the drills and if too small will result in lessened production.

One of the objects of my'invention is to provide a pneumatically-operated tool of the portable type with a pneumatically-operated feed mechanism.

Another object is to provide such a toolwith means by which the operator may quickly mount the same in a fixture for aligning the tool with the-work. These and other objects are accomplished by the construction hereinafter more fully described and illustrated in the accompanying drawing, in which Figure 1 is a side view of the improved air drill shown in relation to the aligning fixture and a work piece;

Figure 2 is a longitudinal section through the feeding mechanism;

Figure 3 is a transverse section on the line 33 of Figure 2.

Referring to the drawing, l represents generally a portable air drill having a main body portion H containing a suitable air operated motor of any suitable type and indicated generally by the reference character H. At the forward end of the body there is a rotatable chuck IQ for holding a drill I3, while at the opposite end of the body there is threadedly secured thereto a housing l4 having the pistol grip handle I5 depending therefrom.

Extending lengthwise of the handle I5 is a main air passageway l5 communicating with a transverse" passageway l1 leading to the air motor within the body M. i8 is a valve longitudinally slidable within a lock nut bushing lfi'threadedly secured at 20 to the handle and having a head 2| sealingly engaging the handle by means of a gasket 22. The bushing has the diametrically opposed openings 23 which are normally closed by the cylindrical portion 24 of the valve. The valve is maintained in closed position by a spring 25 and can be moved to open position by manual pressure on the button which moves the valve against the action of the spring to bring the annular groove 25 in the valve'into alignment with the openings 23. An inlet opening 21 at the bottom of the-handle may be suiably connected to 'a source of air pressure, not shown.

The main passageway 15 communicates through passageway 28 and 29 in the housin M to a. small 'port iifl leading into the longitudinally extending cylinder 3|. This port is adjustably controlled by a needle valve 32 threadedly engaging the housing and secured in adjusted position by a lock nut 33. Within the cylinder 3| there is a piston 34 having an annular packing member 35 secured thereto by means of a nut 36 on the cen tral rod 31. The inner end of this rod has an enlarged head 38 and a projecting portion 39 of smaller diameter. A sleeve 40 surrounds the head 38 and extends longitudinally in the cylinder. 3i.through an opening in thethreaded cap 42 which closes the rear end of the cylinder. A coil spring 44 surrounds th sleeve 40 and serves to normally urge the piston 34 to the left, as shown in Figure 2. Within the sleeve 42 is a slidable -rod 45 having a projection 46 of smaller diameter on its inner end. A coil spring 41 is arranged within the sleeve surrounding the projections 39 and 46 respectively. The rod 45 extends through the sleeve 40 and is retained within the sleeve by a retainer ring 43 which engages the.

annular shoulder 48 on the rod 45. At the outer end of the rod 45 there is a projection 49 of smaller diameter which is adapted to enter a recess or aperture 50 in a suitably arranged backing bracket 5 I.

r The portabl air drill, as hereinbefore described,

operator first inserts the small end 49 of the rod 45 in the aperture 50 of the backing bracket 5| and then moves the portable drill lil rearwardly which is permitted by the compression of the small spring 41. The drill l3 may then be inserted within the bushing 54 whereupon the spring 41 will urge the device forwardly so that the drill engag-es the Work piece. The operator then depresses the button 25' which permits air pressure to pass through passageways l6 and i! into the air motor and rotate the drill. passageway I6 is by-passed through passageways 28, 29 and 30 into the cylinder 3|. AS the pressure builds up in the cylinder, the piston 34 is moved rearwardly within its cylinder until the lost motion between the rod 45 and sleeve 40 is taken up by the contact of the ends of projections 46 and 39. Thereafter, since the rod 45 rests At the same time air from r against the fixed abutment of the backing bracket 5|, additional pressure built-up within the'cylinder causes the entire drill assembly to move forwardly and feed the drill into the work piece. The rate of feed may be controlled by the adjustment of the needle valve 32. As soon as the drilling operation is completed, the operator releases the control button 25 and manually withdraw the drill through the bushing 54 by pressing the drill assembly rearwardly and then removes the rod 45 from the backing bracket, whereupon the sequence of operations is again repeated with the tool arranged in position for drilling the next hole.

What I claim as my invention is:

1. In a pneumatically-operated portable tool, the combination with a casing, a tool rotatably supported therein and a pneumatically-operated motor for said rotatable tool, of a cylinder arranged longitudinally within said casing, a piston in said cylinder, a member projecting through said casing, a telescoping member between said projecting member and said piston providing a limited lost motion connection therebetween, and means for connecting said cylinder to a source of pneumatic pressure to cause relative longitudinal feedtween the inner end of said rod and said piston, a

spring surrounding said sleeve between said piston and said casing, means for limiting the longitudinal movement between said rod and sleeve, and means for connecting said cylinder to a source of pneumatic pressure to cause relative longitudinal feeding movement between said projecting member and said casing.

3. In a pneumatically-operated portable tool, the combination with a casing, a tool rotatably supported therein and a pneumatically-operated motor for said rotatable tool, of a cylinder coaxial with said rotating tool, a piston in said cylinder, a sleeve connected to said piston and projecting rearwardly through said casing, a rod slidable within said sleeve, a spring within said sleeve between the inner end of said rod and said piston, a spring surrounding said sleeve between'said piston and said casing, means for limiting the longitudinal movement between said rod and sleeve, a handle extending transversely of said casing having a fluid passageway connected to said motor and to said cylinder, a manuallyoperated valve in said passageway, and an adjustable metering valve between said fluid passageway and said cylinder.

ARTHUR E. SHERMAN. 

